This invention relates to semiconductor device encapsulations, and particularly encapsulations of the chip carrier type.
Semiconductor chip carriers have been standardized in several designs, including both leaded and leadless types, and in several standard configurations and dimensions. Generally, the carrier type packages are extremely compact, designed for high-density applications. In particular, they utilize close center-to-center lead spacings, typically in the range of 20 to 100 mils. Of particular interest are chip carriers having external metal leads arranged in parallel relation on the periphery of the molded body of the chip carrier. The external leads typically are arranged on all four sides of a rectilinear, usually square, configuration.
Because of the close spacing of the lead members and the small size of chip carriers, the external lead members are extremely susceptible to deformation and damage during the fabrication and assembly processes which render their attachment to circuit boards and the like, particularly by automatic means, difficult and costly. The standards imposed on chip carrier designs require external lead members having some length and terminating in a distinctive arrangement usually referred to as a "footprint". This footprint matches the contact areas on a circuit board or other type of mounting medium. Deflection or other deformation of the external lead members alters the footprint, rendering assembly into circuit apparatus difficult, if not impossible. Correction of such deformation is difficult because of the small size of the external leads and their close proximity to the body of the chip carrier.
Accordingly, an object of this invention is an arrangement which precludes deformation of the external leads on a chip carrier once they have been shaped and formed. An ancillary object is an arrangement which does not substantially increase the size of the chip carrier while providing protection for the formed external leads.